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The Semantic Web

In the early stages of the World Wide Web (web) it was necessary to develop standards to view web content (HTML language) and to create communication channels (N-Tier applications, email, ftp, etc.). As the web started to be the world’s largest knowledge base, accessible world wide, it became important to develop tools to transfer knowledge between cultures. However, it is still not possible for applications and agents to interoperate with other applications and agents without having a predefined, human created common framework of the meaning of the information being transferred on both sides. Semantic Web (SW) alleviates this problem by providing a common framework that allows data to be shared and reused across application, enterprise, and community boundaries [W3C Semantic Web, 2005].

In his vision of the SW, Tim Berners-Lee in [Berners-Lee & Fischetti 1999] says:

"I have a dream for the Web [in which computers] become capable of analyzing all the data on the Web – the content, links, and transactions between people and computers. A ‘Semantic Web’, which should make this possible, has yet to emerge, but when it does, the day-to-day mechanisms of trade, bureaucracy and our daily lives will be handled by machines talking to machines. The ‘intelligent agents’ people have touted for ages will finally materialize."

The SW attempts to create a universal platform for data exchange. The SW aims to transform web content expressed in natural language, into a form that can be understood, interpreted and used by software agents, thus permitting them to find, share, integrate and extract information more easily. As SW is an evolving technology, some elements of the SW are expressed as prospective future possibilities that have yet to be implemented or realized, see [Shadbolt et al., 2006] for more details. Other elements were implemented and expressed in formal specifications and became known as ontology languages. An ontology typically consists of a hierarchical description of important concepts in a domain, along with descriptions of the properties of (the instances of) each concept [Horrocks & Patel-Schneider, 2003]. Ontologies will be discussed in more detail later in this chapter.

The SW is not different from the current World Wide Web (Web). SW enhances the Web by adding more utilities. People, who work in certain fields like research or domains like medicine, music etc., agree on common schemes (ontologies) for representing information they care about. As the Web allows more groups from different cultures and countries to develop these taxonomies, SW tools allow them to map their ontologies and translate their terms; gradually expanding the number of people and communities whose Web software can understand one another automatically [Lee et al., 2007].

A visible example but limited in scope is the social networks websites like Myspace and Flickr where sets of custom tags available for people to use. In these schemes, people select common terms (tags) to describe the content they publish on the Web. This allows Web software to understand the tagged information.

[Shadbolt et al., 2006] in their vision towards a Semantic Web they believe that people and organizations should be obliged to make their data available, this can be driven by collaborative tools and communities of practices, also businesses could make product details available, etc. Those collected information can be then managed and linked into ontologies and integrated and reused by different applications.

The first standard ontology language that defined logical and semantic relations is Resource Description Framework (RDF) and RDF Schema (RDFS) which is the notation for RDF [W3C Semantic Web, 2005]. The current evolution of the SW ontology languages is the Web Ontology Language (OWL). Ontology languages intend to formally describe concepts, terms, and relationships within a given problem domain [W3C Semantic Web, 2005].

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